Separator and fuel cell

ABSTRACT

A separator ( 41 ) for use in a fuel cell stack has an anode facing plate ( 44 ), a cathode facing plate ( 42 ), and an intermediate plate ( 45 ). The intermediate plate ( 45 ) has an air supply through-hole ( 452   a ), an air discharge through-hole ( 452   b ), a hydrogen supply through-hole ( 454   a ), and a hydrogen discharge through-hole ( 454   b ). The intermediate plate ( 45 ) also has through-holes ( 452   c   1, 452   d   1, 452   e   1 , and  452   f   1 ). The air supply through-hole ( 452   a ) is in communication with the through-hole ( 452   c   1 ), the air discharge through-hole ( 452   b ) with the through-hole ( 452   d   1 ), the hydrogen supply through-hole ( 454   a ) with the through-hole ( 452   e   1 ), and the hydrogen discharge through-hole ( 454   b ) with the through-hole ( 452   f   1 ), respectively via communication passages ( 452   c   2, 452   d   2, 452   e   2 , and  452   f   2 ) formed in the intermediate plate ( 45 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of InternationalApplication No. PCT/IB2007/000475, filed Feb. 27, 2007, and claims thepriority of Japanese Application No. 2006-067565, filed Mar. 13, 2006,the contents of both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a separator and a fuel cell having theseparator.

2. Description of the Related Art

Fuel cells, which generate electricity through an electrochemicalreaction between hydrogen and oxygen, are attracting attention as energysources. A fuel cell has a stack structure in which membrane-electrodeassemblies, each having an anode (hydrogen electrode) and a cathode(oxygen electrode) on both sides of an electrolyte membrane that hasproton conductivity, and separators are stacked alternately (the fuelcell having such a stack structure is hereinafter referred to also as“fuel cell stack”).

JP-A 2004-6104 describes a separator having a fuel gas plate that facesan anode (hereinafter referred to as “anode facing plate”), an oxidantgas plate that faces a cathode (hereinafter referred to as “cathodefacing plate”), and an intermediate plate disposed between these plates.In the separator, each gas plate has a through-hole and a gascommunication hole, and the intermediate plate has a delivery passagefor delivery of a fuel gas or an oxidant gas from the gas communicationhole to the through-hole of each gas plate.

A load is applied to the fuel cell stack in the stacking direction ofthe stack structure, to prevent deterioration in cell performance due toan increase in contact resistance at any point in the stack structureand to prevent gas leakage.

In the separator described in JP-A-2004-6104, however, the deliverypassage passes through the intermediate plate in the thicknessdirection, and thus the rigidity against the loads applied verticallywith respect to the surface of the separator, that is, in the stackingdirection of the stack structure, is relatively low at a portion of theintermediate plate where the gas delivery passage is formed.

SUMMARY OF THE INVENTION

The present invention increases the rigidity against the loads appliedvertically to the surface of a separator that is used in a fuel cellstack having an anode facing plate, a cathode facing plate, and anintermediate plate.

A first aspect of the invention provides a separator for use in a fuelcell having a stack structure in which a plurality of membrane-electrodeassemblies are stacked with the separators interposed therebetween. Eachmembrane-electrode assembly has an electrolyte membrane and electrodesdisposed on both sides of the electrolyte membrane. The separatorincludes: two electrode facing plates that face the respectiveelectrodes of the membrane-electrode assembly and an intermediate plateinterposed between the two electrode facing plates. The two electrodefacing plates and the intermediate plate each have a first through-holethat allows a reaction gas to be supplied to the membrane-electrodeassembly, or a discharge gas discharged from the membrane-electrodeassembly, to flow in the stacking direction of the stack structure. Thefirst through-holes of the two electrode facing plates and theintermediate plate overlap with each other when viewed in the stackingdirection. One of the two electrode facing plates and the intermediateplate each have a second through-hole that allows at least the reactiongas to be supplied, or the discharge gas to be discharged, verticallywith respect to the membrane-electrode assembly. The secondthrough-holes of the one of the two electrolyte facing plates and theintermediate plate overlap with each other as viewed in the stackingdirection. The intermediate plate has a communication passage thatallows communication between the first through-hole and the secondthrough-hole in the intermediate plate. The dimension of thecommunication passage in the thickness direction of the intermediateplate is smaller than the thickness of the intermediate plate.

In the first aspect of the invention, the intermediate plate has asecond through-hole and a communication passage, in place of the gasdelivery passage in the intermediate plate of the separator described inJP-A-2004-6104 mentioned above. The dimension of the communicationpassage in the thickness direction of the intermediate plate is smallerthan the thickness of the intermediate plate, and the communicationpassage does not pass through the intermediate plate in the thicknessdirection. Thus, the rigidity against loads applied vertically to thesurface of the separator can be increased, compared to the case where agas delivery passage passes through the intermediate plate in thethickness direction.

The communication passage may be a through-hole that passes through theinside of the intermediate plate in the direction perpendicular to thestacking direction of the stack structure.

In this way, the diameter of the communication passage can be madelargest without the communication passage passing through theintermediate plate in the thickness direction.

In the separator described above, the two electrode facing plates andthe intermediate plate may be bonded together using a bonding agent.

In the separator of JP-A-2004-6104 described above, in which theintermediate plate has a gas delivery passage that passes through theintermediate plate in the thickness direction, if an anode facing plate,a cathode facing plate, and an intermediate plate are bonded togetherusing a bonding agent such as a brazing material or an adhesive, thebonding agent is squeezed into the gas delivery passage. This reducesthe cross-sectional area of the gas delivery passage and a desired gasflow rate cannot be achieved. In the first aspect of the invention,however, a gas delivery passage does not pass through the intermediateplate in the thickness direction; thus, the bonding agent is notsqueezed into the gas delivery passage. As a result, the cross-sectionalarea of the communication passage is not reduced and a desired gas flowrate can be achieved.

In the separator described above, the intermediate plate may be made ofresin, and the bonding agent may be an adhesive.

In the first aspect of the invention, the intermediate plate is made ofresin. Thus, the weight of the separator can be reduced, compared to thecase where the intermediate plate is made of metal. Another advantage tousing a resin member is that a resin member is easier to process than ametal member.

Alternatively, the two electrode facing plates and the intermediateplate may be made of metal, and the bonding agent may be a brazingmaterial.

In this way, the strength of the fuel cell can be improved, compared tothe case where the intermediate plate is made of resin and the bondingagent is an adhesive.

In addition to the constitution as a separator described above, thepresent invention can be implemented as a fuel cell stack having theseparator.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of theinvention will become apparent from the following description ofpreferred embodiments with reference to the accompanying drawings,wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a perspective view illustrating the general construction of afuel cell stack 100 according to an embodiment of the present invention;

FIGS. 2A, 2B, 2C and 2D are plane views of components of a separator 41;

FIG. 3 is a plane view of the separator 41;

FIGS. 4A and 4B are explanatory views of a MEGA seal gasket 46;

FIGS. 5A and 5B are explanatory views of the cross-sectional structureof a fuel cell module 40;

FIGS. 6A, 6B, 6C and 6D are plane views of components of a separator 41Aas a comparative example;

FIGS. 7A and 7B are explanatory views of the cross-sectional structureof a fuel cell module 40A as a comparative example; and

FIG. 8 is an explanatory view illustrating another effect of theembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view illustrating the general construction of afuel cell stack 100 in an embodiment of the present invention. The fuelcell stack 100 has a stack structure in which a plurality of cells forgenerating electricity through an electrochemical reaction betweenhydrogen and oxygen are stacked together with separators interposedtherebetween. Each cell has an anode, a cathode, and an electrolytemembrane having proton conductivity interposed therebetween as describedlater. In this embodiment, polymer electrolyte membranes are used as theelectrolyte membranes. Instead of the polymer electrolyte membranes,other electrolytes such as a solid oxide and the like may be used. Also,in this embodiment, the separator has a three-layer structure, asdescribed later, and is formed with a passage for hydrogen as a fuel gasto be supplied to the anode, a passage for air as an oxidant gas to besupplied to the cathode, and a passage for coolant. A suitable number ofcells may be stacked according to the output power required of the fuelcell stack 100 for a given application.

In the fuel cell stack 100, an end plate 10, an insulating plate 20, acurrent collecting plate 30, a plurality of fuel cell modules 40, acurrent collecting plate 50, an insulating plate 60, and an end plate 70are stacked in this order from one end to the other. These members havesupply ports, discharge ports and passages (all not shown) that allowhydrogen as a fuel gas, air as an oxidant gas, and coolant to flowthrough the fuel cell stack 100. The hydrogen is supplied from ahydrogen tank (not shown). The air and the coolant are pressurized andsupplied by pumps (not shown). Each fuel cell module 40 is constitutedof a separator 41 and a MEGA seal gasket 46 in which amembrane-electrode assembly and a gasket are integrated, which aredescribed later. The fuel cell module 40 is described later. The term“MEGA” as used herein is an abbreviation for “Membrane Electrode Gasdiffusion layer Assembly”, and refers to a membrane-electrode assemblythat is an electrolyte membrane with a catalyst layer and a gasdiffusion layer formed on both surfaces.

The fuel cell stack 100 also has tension plates 80 as shown in thedrawing. A pressing force is applied to the fuel cell stack 100 in thestacking direction of the stack structure, to prevent deterioration incell performance due to an increase in contact resistance at any pointin the stack structure, and to prevent gas leakage. By fixing thetension plates 80 to the end plates 10 and 70 at both ends of the fuelcell stack 100 with bolts 82, each fuel cell module 40 is tightened witha predetermined tightening force in the stacking direction.

The end plates 10 and 70, and the tension plates 80 are made of a metalsuch as steel to ensure rigidity. The insulating plates 20 and 60 aremade of an insulating material such as rubber or resin. The currentcollecting plates 30 and 50 are made of a gas-impermeable conductivematerial such as densified carbon or copper. Each of the currentcollecting plates 30 and 50 has an output terminal (not shown) so thatthe electric power generated in the fuel cell stack 100 can be outputtherefrom.

As described before, each fuel cell module 40 has a separator 41 and aMEGA seal gasket 46. The separator 41 and the MEGA seal gasket 46 aredescribed below.

FIGS. 2A to 2D are plane views of components of the separator 41. Asshown in the drawings, the separator 41 is constituted of a cathodefacing plate 42, an anode facing plate 44, an intermediate plate 45, anda coolant passage forming member 43.

In this embodiment, the cathode facing plate 42 and the anode facingplate 44 are flat and have the same square outer shape. These flatplates are made of stainless steel. The coolant passage forming member43 is also made of stainless steel. The cathode facing plate 42, theanode facing plate 44 and the coolant passage forming member 43 may bemade of other metals such as titanium or aluminum instead of stainlesssteel. Because these members are exposed to the coolant as describedlater, anti-corrosive metals may also be used.

The intermediate plate 45 has the same outer shape as the cathode facingplate 42 and the anode facing plate 44. The intermediate plate 45 ismade of resin. Suitable resins that may be used to make the intermediateplate include, but are not limited to, polypropylene, polyethylene,polyamide, polyurethane and polyethylene terephthalate may be used.Because the separator 41 is required to have a low electricalresistance, conductive resin may be used for the intermediate plate 45.

FIG. 2A is a plane view of the cathode facing plate 42, which contactsthe cathode side surface of the MEGA seal gasket 46 to be describedlater. As shown in the drawing, the cathode facing plate 42 has an airsupply through-hole 422 a, a plurality of air supply ports 422 i, aplurality of air discharge ports 422 o, an air discharge through-hole422 b, a hydrogen supply through-hole 424 a, a hydrogen dischargethrough-hole 424 b, a coolant supply through-hole 426 a, and a coolantdischarge through-hole 426 b. In this embodiment, the air supplythrough-hole 422 a, the air discharge through-hole 422 b, the hydrogensupply through-hole 424 a, the hydrogen discharge through-hole 424 b,the coolant supply through-hole 426 a, and the coolant dischargethrough-hole 426 b are generally rectangular, and the air supply ports422 i and the air discharge ports 422 o are circular and have the samediameter.

FIG. 2B is a plane view of the anode facing plate 44, which contacts theanode side surface of the MEGA seal gasket 46, to be described later. Asshown in the drawing, the anode facing plate 44 has an air supplythrough-hole 442 a, an air discharge through-hole 442 b, a hydrogensupply through-hole 444 a, a plurality of hydrogen supply ports 444 i, aplurality of hydrogen discharge ports 444 o, a hydrogen dischargethrough-hole 444 b, a coolant supply through-hole 446 a, and a coolantdischarge through-hole 446 b. In this embodiment, the air supplythrough-hole 442 a, the air discharge through-hole 442 b, the hydrogensupply through-hole 444 a, the hydrogen discharge through-hole 444 b,the coolant supply through-hole 446 a, and the coolant dischargethrough-hole 446 b are generally rectangular, and the hydrogen supplyports 444 i and the hydrogen discharge ports 444 o are circular and havethe same diameter.

FIG. 2C is an explanatory view of the intermediate plate 45. The drawingshows a plane view, a side view, and a cross-sectional view taken alongthe line I-I of FIG. 2C, of the intermediate plate 45. The structure ofthe intermediate plate 45 is the characteristic of the presentinvention, and described in detail later in contrast to a comparativeexample.

As shown in the drawing, the intermediate plate 45 has an air supplythrough-hole 452 a, an air discharge through-hole 452 b, a hydrogensupply through-hole 454 a, and a hydrogen discharge through-hole 454 b.In addition, the intermediate plate 45 has a plurality of through-holes452 c 1, a plurality of through-holes 452 d 1, a plurality ofthrough-holes 452 e 1, and a plurality of through-holes 452 f 1 in thevicinity of the air supply through-hole 452 a, the air dischargethrough-hole 452 b, the hydrogen supply through-hole 454 a, and thehydrogen discharge through-hole 454 b, respectively. These through-holesare circular and have the same diameter.

The plurality of through-holes 452 c 1 are in communication with the airsupply through-hole 452 a via a plurality of communication passages 452c 2 formed inside the intermediate plate 45, respectively. The pluralityof through-holes 452 d 1 are in communication with the air dischargethrough-hole 452 b via a plurality of communication passages 452 d 2formed inside the intermediate plate 45, respectively. The plurality ofthrough-holes 452 e 1 are in communication with the hydrogen supplythrough-hole 454 a via a plurality of communication passages 452 e 2formed inside the intermediate plate 45, respectively. The plurality ofthrough-holes 452 f 1 are in communication with the hydrogen dischargethrough-hole 454 b via a plurality of communication passages 452 f 2formed inside the intermediate plate 45, respectively.

The intermediate plate 45 also has a coolant flowing part 456 thatallows the coolant to flow through the intermediate plate 45 in theseparator 41. The transverse length of the coolant flowing part 456 inthe drawing is the same as the length W3 from the outer side of thecoolant supply through-hole 446 a to the outer side of the coolantdischarge through-hole 446 b shown in FIG. 2B, and the vertical lengthis the same as the length W2, or the vertical length of the coolantsupply through-hole 446 a and the coolant discharge through-hole 446 bshown in FIG. 2B.

FIG. 2D shows a plane view and a side view of the coolant passageforming member 43. A plane view and a side view of the coolant passageforming member 43 are shown on the left side and the right side,respectively, of FIG. 2D.

As shown in the drawing, the coolant passage forming member 43 hasrectangular projections and depressions arranged alternately in crosssection. The transverse length of the coolant passage forming member 43in the drawing is the same as the length W1 from the inner side of thecoolant supply through-hole 446 a to the inner side of the coolantdischarge through-hole 446 b shown in FIG. 2B, and the vertical lengthis the same as the vertical length W2 of the coolant supply through-hole446 a and the coolant discharge through-hole 446 b. The height of thecoolant passage forming member 43 is approximately the same as thethickness t of the intermediate plate 45. In the manufacturing processof the separator 41, the coolant passage forming member 43 is placed ina region between the coolant supply through-hole 426 a and the coolantdischarge through-hole 426 b of the cathode facing plate 42, and in aregion between the coolant supply through-hole 446 a and the coolantdischarge through-hole 446 b of the anode facing plate 44.

FIG. 3 is a plane view of the separator 41. The separator 41 is formedby placing the coolant passage forming member 43 at the center of thecoolant flowing part 456 of the intermediate plate 45, and then bondingthe cathode facing plate 42, the anode facing plate 44 and theintermediate plate 45 with an adhesive. Here, the separator 41 is shownas viewed from the anode facing plate 44 side.

As can be understood from the drawing, the air supply through-holes 442a, 452 a, and 422 a are formed in the same position through the anodefacing plate 44, the intermediate plate 45, and the cathode facing plate42. The air discharge through-holes 442 b, 452 b and 422 b are formed inthe same position. The hydrogen supply through-holes 444 a, 454 a, and424 a are formed in the same position. The hydrogen dischargethrough-holes 444 b, 454 b, and 424 b are formed in the same position.These through-holes function as the first through-hole of the invention.

The hydrogen supply ports 444 i and the through-holes 452 e 1 are formedin the same positions through the anode facing plate 44 and theintermediate plate 45. The hydrogen discharge ports 444 o and thethrough-holes 452 f 1 are formed in the same positions. The air supplyports 422 i and the through-holes 452 c 1 are formed in the samepositions through the cathode facing plate 42 and the intermediate plate45. The air discharge ports 422 o and the through-holes 452 d 1 areformed in the same positions. These through-holes function as the secondthrough-hole of the invention.

The coolant supply through-holes 446 a and 426 a are formed in the sameposition through the anode facing plate 44 and the cathode facing plate42. The coolant discharge through-holes 446 b and 426 b are formed inthe same position.

FIGS. 4A and 4B are explanatory views of the MEGA seal gasket 46. FIG.4A is a plane view of the MEGA seal gasket 46 as viewed from the cathodeside. FIG. 4B is a cross-sectional view taken along the line I-I of FIG.4A.

As shown in the drawings, the MEGA seal gasket 46 has a MEGA section 461and a frame 460 surrounding and supporting the MEGA section 461.Although silicone rubber is used for the frame 460 in this embodiment,the present invention is not limited thereto. Other materials having gasimpermeability, elasticity, and heat resistance may also be used.

The MEGA section 461 is a membrane-electrode assembly in which a cathodediffusion layer 49 c is stacked on a cathode catalyst layer 48 c andover one surface (cathode side surface) of an electrolyte membrane 47and an anode diffusion layer 49 a is stacked an anode catalyst layer 48a over the other surface (anode side surface) of the electrolytemembrane 47 as shown in FIG. 4B. In this embodiment, carbon porousbodies are used as the anode diffusion layer 49 a and the cathodediffusion layer 49 c. Also, in this embodiment, metal porous layers 49,which function as gas passage layers for allowing hydrogen and air toflow when the MEGA seal gasket 46 is stacked on the separator 41, areprovided on both sides of the MEGA section 461. With this constitution,the gasses may be supplied as diffused efficiently over the entiresurfaces of the anode and the cathode. For the gas passage layers, othermaterials having electrical conductivity and gas diffusibility such ascarbon may be used in place of the metal porous bodies.

The frame 460 has an air supply through-hole 462 a, an air dischargethrough-hole 462 b, a hydrogen supply through-hole 464 a, a hydrogendischarge through-hole 464 b, a coolant supply through-hole 466 a, and acoolant discharge through-hole 466 b as in the case with the separator41 as shown in FIG. 4A. Sealing parts 468 are integrally provided aroundthe through holes and around the MEGA section 461 to form seal lines SLshown by thin lines in FIG. 4A. That is, the frame 460 functions as agasket that prevents leakage of hydrogen, oxygen and coolant. The frame460 is formed by, for example, injection molding.

FIGS. 5A and 5B are explanatory views of the cross-sectional structureof the fuel cell module 40. FIG. 5A is a cross-sectional view takenalong the line I-I of FIG. 3, and FIG. 5B is a cross-sectional viewtaken along the line II-II of FIG. 3.

In the MEGA seal gasket 46, the metal porous layer 49 on the anode sideof the MEGA section 461 contacts the anode facing plate 44 of theseparator 41 when the MEGA seal gasket 46 and the separator 41 arestacked together. Also, the metal porous layer 49 on the cathode side ofthe MEGA section 461 contacts the cathode facing plate 42 of theseparator 41 when the MEGA seal gasket 46 and the separator 41 arestacked together. The sealing parts 468 contact the cathode facing plate42 and the anode facing plate 44 to form the seal lines SL shown in FIG.4A.

As shown by arrows in FIG. 5A, in the fuel cell module 40, air suppliedfrom the air supply through-hole 442 a of the anode facing plate 44 isbranched in the air supply through-hole 452 a of the intermediate plate45, and passes through the communication passage 452 c 2 and thethrough-hole 452 c 1 to be supplied from the air supply port 422 i ofthe cathode facing plate 42 vertically with respect to the surface ofthe MEGA section 461. The air then flows in the metal porous layer 49 onthe cathode side and in the cathode diffusion layer 49 c, and as shownin FIG. 5B, is discharged from the air discharge port 422 o of thecathode facing plate 42 vertically with respect to the surface of theMEGA section 461, passes through the through-hole 452 d 1, thecommunication passage 452 d 2, and the air discharge through-hole 452 bof the intermediate plate 45, and is discharged from the air dischargethrough-hole 442 b of the anode facing plate 44.

Here, only the flow of the air to be supplied to the cathode of the MEGAsection 461 has been described. The hydrogen to be supplied to the anodeflows in the same way.

Next, the separator 41A and a fuel cell module 40A, as a comparativeexample, will be described to clarify the effect of the embodimentdescribed above. The construction of the fuel cell stack in thecomparative example is the same as that of the fuel cell stack 100 ofthe embodiment except for the separator 41A.

FIGS. 6A to 6D are plane views of components of the separator 41A as acomparative example. The separator 41A is constituted of componentsstacked together as in the case with the separator 41. The separator 41Ais constituted of a cathode facing plate 42, an anode facing plate 44,an intermediate plate 45A, and a coolant passage forming member 43. Thecathode facing plate 42, the anode facing plate 44, and the coolantpassage forming member 43 are the same as those in the separator 41 inthe embodiment described above. The intermediate plate 45A is partlydifferent from the separator 41 in the embodiment described above. Thus,hereinafter, the cathode facing plate 42, the anode facing plate 44, andthe coolant passage forming member 43 are not described, and only theintermediate plate 45A is described.

As shown in the drawing, the intermediate plate 45A has an air supplythrough-hole 452 a, an air discharge through-hole 452 b, a hydrogensupply through-hole 454 a, and a hydrogen discharge through-hole 454 b,as in the case with the intermediate plate 45 in the embodimentdescribed above. The air supply through-hole 452 a has a plurality ofair supply passage forming portions 452 c that allow air to flow fromthe air supply through-hole 452 a to the plurality of air supply ports422 i of the cathode facing plate 42, respectively, in place of thethrough-holes 452 c 1 and the communication passages 452 c 2 in theembodiment described above. The air discharge through-hole 452 b has aplurality of air discharge passage forming portions 452 d that allow airto flow from the plurality of air discharge ports 422 o of the cathodefacing plate 42 to the air discharge through-hole 452 b, in place of thethrough-holes 452 d 1 and the communication passages 452 d 2 in theembodiment described above. The hydrogen supply through-hole 454 a has aplurality of hydrogen supply passage forming portions 452 e that allowhydrogen to flow from the hydrogen supply through-hole 454 a to theplurality of hydrogen supply ports 444 i of the anode facing plate 44,respectively, in place of the through-holes 452 e 1 and thecommunication passages 452 e 2 in the embodiment described above. Thehydrogen discharge through-hole 454 b has a plurality of hydrogendischarge passage forming portions 452 f that allow hydrogen to flowfrom the plurality of hydrogen discharge ports 444 o of the anode facingplate 44 to the hydrogen discharge through-hole 454 b, in place of thethrough-holes 452 f 1 and the communication passages 452 f 2 in theembodiment described above. The air supply passage forming portions 452c, the air discharge passage forming portions 452 d, the hydrogen supplypassage forming portions 452 e, and the hydrogen discharge passageforming portions 452 f pass through the intermediate plate 45A in thethickness direction.

FIGS. 7A and 7B are explanatory views of the cross-sectional structureof the fuel cell module 40A as a comparative example. FIG. 7Acorresponds to FIG. 5A that is a cross-sectional view taken along theline I-I of FIG. 3, and FIG. 7B corresponds to FIG. 5B that is across-sectional view taken along the line II-II of FIG. 3.

The MEGA seal gasket 46 is the same as that in the embodiment describedabove.

As shown by arrows in FIG. 7A, in the fuel cell module 40A, air suppliedfrom the air supply through-hole 442 a of the anode facing plate 44 isbranched in the air supply through-hole 452 a of the intermediate plate45, and passes through the air supply passage forming portion 452 c tobe supplied from the air supply port 422 i of the cathode facing plate42 vertically with respect to the surface of the MEGA section 461. Theair then flows in the metal porous layer 49 on the cathode side and inthe cathode diffusion layer 49 c, and as shown in FIG. 7B, is dischargedfrom the air discharge port 422 o of the cathode facing plate 42vertically with respect to the surface of the MEGA section 461, passesthrough the air discharge passage forming portion 452 d and the airdischarge through-hole 452 b of the intermediate plate 45, and isdischarged from the air discharge through-hole 442 b of the anode facingplate 44. Here, only the flow of the air to be supplied to the cathodeof the MEGA section 461 has been described. The hydrogen to be suppliedto the anode flows in the same way.

In the embodiment and the comparative example described above, the areasin the ellipse of the broken line in FIGS. 5A and 7A are specificallyfocused. The separator 41, or the separator 41A, and the MEGA sealgasket 46 are stacked together, and a predetermined load in the stackingdirection is applied thereto. Then, in the embodiment described above,because the intermediate plate 45 is formed with the communicationpassages 452 c 2, the load applied to the separator 41 in the stackingdirection by the sealing parts 468 is supported by the anode facingplate 44 and the intermediate plate 45, as shown in FIG. 5A. Incontrast, in the comparative example, because the intermediate plate 45Ais formed with the air supply passage forming portions 452 c passingthrough the intermediate plate 45A in the thickness direction, the loadapplied to the separator 41A in the stacking direction by the sealingparts 468 of the MEGA seal gasket 46 is supported only by the anodefacing plate 44 and not by the intermediate plate 45A, as shown in FIG.7A. Thus, with the separator 41 of the embodiment described above, therigidity against loads applied vertically to the surface of theseparator is increased, compared to the separator 41A of the comparativeexample.

FIG. 8 is an illustrates another effect of the embodiment describedabove. The upper part of FIG. 8 shows a cross-sectional view of a partof the cathode facing plate 42, the intermediate plate 45A, and theanode facing plate 44 in the comparative example. The lower part of FIG.8 shows a cross-sectional view of the separator 41A formed by bondingtogether the cathode facing plate 42, the intermediate plate 45A, andthe anode facing plate 44 using an adhesive 450.

When the adhesive 450 is applied to both surfaces of the intermediateplate 45A and the cathode facing plate 42 and the anode facing plate 44are bonded to the intermediate plate, as shown in the upper part of FIG.8, the adhesive 450 may be squeezed into the hydrogen supply passageforming portions 452 e which pass through the intermediate plate 45A inthe thickness direction, as shown in the lower part of FIG. 8. Thisreduces the cross-sectional areas of the passages and a desired gas flowrate may not be achieved. In contrast, the intermediate plate 45 of theembodiment described above has communication passages 452 e 2 which donot pass through the intermediate plate 45 in the thickness direction,as can be understood from the cross-sectional view of the intermediateplate 45 shown in FIG. 2C and so forth. Thus, the adhesive 450 is notsqueezed into the communication passages 452 e 2 when the cathode facingplate 42, the anode facing plate 44, and the intermediate plate 45 arebonded together using the adhesive 450. Thus, the cross-sectional areasof the communication passages 452 e 2 are not reduced by the adhesive450 and a desired gas flow rate can be achieved.

Although an embodiment of the present invention has been describedabove, the present invention is not limited to the described embodiment,and various modifications may be made thereto without departing from theobject thereof. For example, the following modifications can be made.

Although a resin member is used as the intermediate plate 45 and bondedto the cathode facing plate 42 and the anode facing plate 44 using theadhesive 450 in the embodiment described above, the present invention isnot limited thereto. A metal member may be used as the intermediateplate 45, for example, and bonded to the cathode facing plate 42 and theanode facing plate 44 using a brazing material. However, using a resinintermediate plate 45 reduces the weight of the separator 41 and thefuel cell stack 100. Another advantage of a resin member is that it iseasier to process, compared to a metal member.

Although the air supply through-hole 452 a, the air dischargethrough-hole 452 b, the hydrogen supply through-hole 454 a, and thehydrogen discharge through-hole 454 b of the intermediate plate 45 areprovided with the through-holes 452 c 1, 452 d 1, 452 e 1, and 452 f 1,and the communication passages 452 c 2, 452 d 2, 452 e 2, and 452 f 2,respectively, in the embodiment described above, the present inventionis not limited thereto. The various passage forming portions describedabove in the comparative example may be provided for a part of the airdischarge through-hole 452 b, the hydrogen supply through-hole 454 a,and the hydrogen discharge through-hole 454 b.

While the invention has been described with reference to exampleembodiments thereof, it is to be understood that the invention is notlimited to the described embodiments or constructions. To the contrary,the invention is intended to cover various modifications and equivalentarrangements. In addition, while the various elements of the embodimentsare shown in various combinations and configurations, other combinationsand configurations, including more, less or only a single element, arealso within the spirit and scope of the invention.

1. A separator for use in a fuel cell that has a stack structure inwhich a plurality of membrane-electrode assemblies are stacked with theseparators interposed therebetween, each membrane-electrode assemblyhaving an electrolyte membrane and electrodes disposed on both sidesthereof, the separator comprising: two electrode facing plates that facethe respective electrodes of the membrane-electrode assembly; and anintermediate plate interposed between the two electrode facing plates,wherein the two electrode facing plates and the intermediate plate eachhave: a first through-hole through which a reaction gas that is suppliedto the membrane-electrode assembly, or a discharge gas that isdischarged from the membrane-electrode assembly, flows in a stackingdirection of the stack structure, the first through-holes of the twoelectrode facing plates and the intermediate plate overlapping with eachother as viewed in the stacking direction; one of the two electrodefacing plates, and the intermediate plate each have: a secondthrough-hole through which at least the reaction gas is supplied, or thedischarge gas is discharged, perpendicularly with respect to a surfaceof the membrane-electrode assembly, the second through-holes of the oneof the two electrode facing plates and the intermediate plateoverlapping with each other when viewed in the stacking direction; theintermediate plate has a communication passage for communication betweenthe first through-hole and the second through-hole in the intermediateplate; wherein said communication passage is a through-hole that passesthrough an inside of the intermediate plate in a direction perpendicularto the stacking direction of the stack structure, and wherein adimension of the communication passage in a direction of a thickness ofthe intermediate plate is smaller than the thickness of the intermediateplate.
 2. The separator according to claim 1, wherein the two electrodefacing plates and the intermediate plate are bonded together using abonding agent.
 3. The separator according to claim 2, wherein theintermediate plate is made of resin, and the bonding agent is anadhesive.
 4. The separator according to claim 2, wherein theintermediate plate is made of metal, and the bonding agent is a brazingmaterial.
 5. A fuel cell having a stack structure in which a pluralityof membrane-electrode assemblies are stacked with separators interposedtherebetween each membrane-electrode assembly having an electrolytemembrane and electrodes disposed on both sides thereof, wherein: theseparator is the separator according to claim 1.